Estimation of C2H5-Benzenes in Refinery Streams

A simple and direct gas chromatography-mass spectrometry method for routine estimation of C2 H5-alkylbenzenes (or C2-alkylbenzenes), namely, ethylbenzene and m/p- and o-xylenes in the boiling range of 80°C-400°C, including diesel range streams using deuterated ethylbenzene as internal standard has been described. Estimation of C2-alkylbenzenes in feeds and products is important for monitoring the reaction kinetics in certain secondary processes which involve conversion of low value, aromatic-rich diesel range boiling streams to produce aromatic-based petrochemical feedstocks upto xylenes. The method developed takes advantage of chromatographic separation and resolution masses of fragment ions of the compounds of interest for estimation. Linearity in estimation has been established in the range of 300 ppm to 5% (w/w) for ethylbenzene, m/p-xylenes and o-xylenes. Correlation coefficient (R2) value of 0.99 was obtained for the three compounds for calibration mixtures. Total 15 samples obtained from refineries, pilot plant for mono-aromatic enrichment studies, and commercial diesel samples were analyzed by this method for estimation of ethylbenzene, m/p- and o-xylenes content.

Comparison between supercritical carbon dioxide extraction and aqueous surfactant washing of an oily machining waste

Mathematical models are developed to compare aqueous surfactant washing to supercritical carbon dioxide (SCCO2) extraction. These two cleaning processes are potentially competitive technologies which can be used to remove oily contaminants from a solid waste. In both processes, the cleaning efficiency for a batch of waste is evaluated by quantifying the residual oil content in the treated sample. A mass transfer model is used to simulate a semi-continuous washing process, and the experimental data, obtained in a batch operation, are used to estimate the equilibrium parameters in the model. For SCCO2 extraction, a linear desorption model is used to describe the supercritical desorption of oil from the solid phase into the CO2 phase and the simulated results agreed very well with the experimental data. The oil removal in aqueous surfactant washing is viewed to be controlled primarily by the diffusional transport of oil from the interiors of the waste elements to the surface, thus, it can be significantly affected by the size of the particles. A pre-cleaning pulverization is then recommended to improve the cleaning efficiency without increasing any other operation costs. In SCCO2 extraction, the desorption of oil from the solid waste is the controlling step and consequently, the solvent flow rate has no influence on oil removal. Our theoretical studies show that the difference between the cleaning efficiencies of these two technologies is not significant, with the oil concentration in the washing products approximately 5% lower than that in the extraction products.